1. Field of the Invention
The present invention relates to a switching mechanism for optical component employed in a camera or the like to allow switching between a state where an optical component that shields infrared light is on the optical axis and a state where the optical component is off the optical axis, a lens barrel using this switching mechanism, and an imaging device provided with this lens barrel.
2. Description of Related Art
In a video camera and a digital still camera configured to take a moving image and a still image, a lens barrel is provided to a camera main body as an integral part or as a separate component. The lens barrel includes, for example, a lens group furnished with a variable magnification function, a lens group furnished with a function of correcting a field fluctuation associated with a change of magnification or a change of a subject distance are assembled in a cylindrical barrel main body.
In this lens barrel, various filters to adjust an amount of incident light, for example, an infrared light cut filter to shield infrared light is provided on the optical path.
Incidentally, a variety of imaging modes are available with a video camera in recent years. Besides normal imaging, a so-called night-shot imaging mode enabling nighttime imaging is now available in some types of video camera. In the night-shot imaging mode, it is necessary to actively let infrared light in. It is therefore necessary to remove the infrared light cut filter described above from the optical path.
To this end, there has been proposed a lens barrel provided with a switching mechanism for optical component, which is a mechanism that moves the infrared light cut filter to the outside of the optical path. An example of such a lens barrel is described in JP-A-11-194417.
This switching mechanism for optical component includes a type configured in such a manner that switching is made manually and a type configured in such a manner that switching is made electrically using a motor as a drive source. In the case of the manual switching, there is a risk of failure because an extra load may possibly be applied on the mechanical mechanism depending on a manner of operation by the user.
Meanwhile, in the case of the electrical switching, a link mechanism used to transmit drive power from the motor becomes complicated and rattling may possibly occur depending on an assembly accuracy of the link mechanism. Further, because a slightly oversized optical component is used by taking the rattling into account in the case of the electrical switching, the lens barrel itself undesirably becomes larger and more expensive.